E. Nearly Shortest Repeating Substring

#include<iostream>
#include<algorithm>
#include<cstring>
#include<cmath>
using namespace std;
int n, m;
int main()
{
	cin >> n;
	while (n--)
	{
		//string s;
		cin >> m;
		string s;
		cin >> s;
		int res =m;
		for (int i = 1; i <= m; i++)
		{
			int ans = 0;
			if (m%i!= 0)//如果不能整除说明
				//无法拼接成正常的串,直接排除
				continue;
			string ss = s.substr(0, i);//从前往后截取
			for (int j = 0, k = 0; j < m; j++)
			{
				if (s[j] != ss[k++]) ans++;
				if (k >= i)k = 0;//当一段检查完成之后另k=0,检查另一段
				if (ans >1) break;
				//ans只有0,1才是合法的其他直接排除
			}
			if (ans <= 1)
				res = min(res, i);
			ans = 0;
			ss = s.substr(m-i, i);//倒着截取
			for (int j = 0, k = 0; j < m; j++)
			{
				if (s[j] != ss[k++]) ans++;
				if (k >= i)k = 0;
				if (ans >1) break;
			}
			if (ans <= 1)
				res = min(res, i);
		}
		cout << res << endl;
	}
	return 0;
}